This invention relates to a feeding system for a combine and in particular to means for conveying crop material from the harvesting means to the crop processing means.
Although combine field capacities continue to increase and the appetites of their threshing and separating mechanisms grow ever larger, the archaic chain and slat conveyor is still conventionally employed in the feeder house. Such conveyors have a relatively low specific capacity (throughput per unit of width), because of limitations which include an inability to feed positively, and a tendency to backfeeding because of the necessary presence of an at least partially open return side. In addition, the potential for increasing capacity by increasing the linear speed of the conveyor is severly limited by the inherent instability of the conveyor chain.
In recent years, with the adaptation of the combine to corn harvesting and the introduction of the corn head, auger conveyors came into use in association with said corn heads. Partly because the first corn heads were designed to harvest two rows at a time and partly because of the configuration of the conventional transverse threshing cylinder, a pair of side-by-side augers were used to convey the crop material to the threshing cylinder. However in spite of being paired, the individual augers were typically treated as single auger conveyors. Initially, the augers, in their separate troughs, were separated by a dividing wall but it was eventually realized that long stalk material might be better handled with an open center in the conveyor and the dividing wall was lowered, creating an opportunity for crop material to distribute itself across the width of the conveyor and reduce the incidence of plugging. However, the augers remained in side-by-side troughs, the space between their opposing conveying surfaces consequently being at least partially occupied by sheet metal, and much of the potential conveying capacity surrounding the augers was not used. Typically, these augers were journaled at their inlet end in self-aligning bearings and supported towards their delivery ends by their troughs, a design severly limiting rotational speeds and hence conveying capacity. A pair of augers have been placed side by side in a single trough with their flighting overlapping in an attempt to achieve more positive conveying, but such an arrangement sacrifices some of the potential capacity of the conveyor and increases the tendency for crop material to wrap around the augers.
Twin auger conveyors have also been used in feeding the crop processing units in legume harvesters. But in this application, as well as in the corn head, emphasis is placed on avoidance of crushing or restricting the crop material to reduce both plugging and damage to the material itself. And so in these systems, feeding of the crop to the processing unit is not positive or consistent and feeding rate varies greatly with the condition of the material being fed.
The characteristics of single augers, especially when handling homogeneous granular materials in closed housings, are well known and their performance is predictable. But in existing applications, such as the corn and legume harvesters mentioned above, twin augers have been used mainly to provide a "moving floor"-type conveyor for the conveying of crop material, possessing some advantage over the slat conveyor but not intrinsically different in conveying characteristic. Nowhere has there been recognized or realized the potential for positive, compact and efficient conveying of a pair of augers, side by side and fully enclosed, optimally spaced from each other and from the walls of their housing to produce a conveyor of high specific capacity and predictable performance.
In recent years, efforts to develop a successful combine using a longitudinal axial flow rotary crop processing unit have intensified. Such units have a much greater specific capacity than conventional units, and the difficulty of feeding them at full capacity has been a major obstacle in development. Feeding devices not only need greater capacity but, in particular for single rotor configurations, should be capable of delivering material in a relatively narrow stream with an axial component of velocity sufficient that, typically, it can be received by an infeed rotor for distribution around the circumference of the first stage of an axial flow rotary mechanism without energy consuming or capacity reducing major changes in direction.
The large number of patents issuing in recent years in the field of feeding axial flow rotary threshers and separators is evidence that much attention is being given to a difficult problem. But typically in these attempts, chain and slat conveyor feeder houses have been used, and their limitations in this application are soon realized. Apart from the inherent limitations of the slat conveyor as such (outlined above), it is only marginally adaptable to axial feeding of a single rotor longitudinally disposed unit because of the need to converge the stream of crop material from the relatively wide slat to the narrower rotor.
The patents referred to disclose mostly refinements in the juxtaposition of the slat feeding conveyor and the infeed rotor and in the design of the rotor rather than any attack on the more fundamental problem of the feeder conveyor itself, and until the present invention, there has been no evience of a breakthrough in this area.